Electro-optical devices using organic materials have been drawing an increasing amount of attention as next generation devices due to their numerous advantages. In particular, a polymer electronic device using a polymer as an active layer can be easily and economically fabricated through a wet process, can be curved, and thus may be regarded as a new electronic device. However, before commercializing the polymer electronic device, problems of low performance and short device lifetime have to be overcome.
There are two ways to improve the performance of the polymer device, one is to improve the performance of a material applied to the device, and the other is to improve the structure of the device and its fabrication method. However, it may be difficult to synthesize a new material having high performance, and while there have been various attempts to improve structure and fabrication method, no substantial progress has been made. A great deal of current research has aimed at improving device performance by introducing a material having a new function into a conventional device structure, because this enables device performance to be improved more easily and conventional fabrication techniques to be used.
Meanwhile, the polymer electronic device using the polymer as an active layer may have a short lifetime since the polymer used as the active layer is vulnerable to moisture and oxygen. When an electronic device is fabricated and driven, the performance of the device may drastically deteriorate due to the effects of moisture and oxygen on the polymer. In order to improve the performance of the device, oxygen and moisture existing in the device have to be removed during fabrication and prevented from infiltrating from outside.
In order to extend the lifetime of a device, after blocking oxygen and moisture during fabrication, oxygen and moisture should be prevented from infiltrating from the outside using an encapsulation method. However, this method may require complicated fabrication processes and high-priced equipment. Further, while oxygen and moisture may be efficiently prevented from infiltrating from outside, oxygen and moisture that has already infiltrated can not be easily removed during fabrication. Thus, the method is ineffective at extending the lifetime of the device. Accordingly, there is a need to develop new technology capable of easily blocking oxygen and moisture at low cost and removing oxygen and moisture already present to extend the lifetime of a device.
Titanium oxide is a representative metal oxide photocatalyst that is used to remove indoor moisture and disinfect through a photodegradation function. The photocatalyst functions to remove moisture and decompose organic materials through absorption of light, and in particular, the titanium oxide has high electron mobility. This fact suggests that when titanium oxide is appropriately modified to perform new functions, it may be applied to a polymer electronic device. That is, when advantages of titanium oxide are exploited to remove oxygen and moisture and facilitate electron transfer, and its characteristics are changed to apply to a polymer electronic device, the polymer electronic device's problems of poor performance and short lifetime may be overcome.
However, all metal oxide photocatalysts developed thus far, including titanium oxide, are hydrolyzed and gelated so that they are opaque when fabricated, or they take the form of powder. This makes it difficult to fabricate a film using them. Moreover, since a sintering process is performed at a high temperature, it is difficult to apply to a heat-sensitive polymer electronic device. Therefore, there is need of a new material that is capable of overcoming the above problems and facilitating electron transfer and moisture removing effect of titanium oxide, and that can be applied by coating and does not require separate thermal treatment.